Refractor collimnationPosted By jonathan hendrick |
:S Hello out there. I just purchased a used 4" ED refractor and am having troubles with collimnation. I'm using the startest technique with the sun on a ball bearing around 100 feet from the scope. Initially, I noticed some very outstretched difraction patterns (rays) at 9 and 7 o'clock extending from the focused image. Upon defocusing, it was clear that colimnation was the issue as the center spot was nudged to one side and the diffraction rings were noticably brighter in the same area. So far a releif! I then began adjusting the mirror cell. After considerable adjustment, to the point where the bottom of the mirror cell was almost half a centimeter from the tube flange, and the top of the cell was touching, the brightness in the diffraction rings became balance and the bright spot was centered. But, now there is a serious amount of astigmatism showing. The scope will only focus to a cross and opens into slits perpendicuallary oposite to each other on either near side of focus. Astigmatism was not abserved when the collimnation appeared bad, but after tilting the lens cell for best diffraction uniformity it is evident. Do I have an astigmatism issue, or am I not collimnating correctly?
